Method for preparing phosphate at low temperature by directly utilizing lithium extraction tailings
Patent Information
- Application Number
- CN202510937423.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-07-08
- Publication Date
- 2025-11-07
Smart Images
Figure CN120903451A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the technical field of battery material recycling, and particularly relates to a method for directly preparing phosphate at low temperature by using lithium extraction tailings. BACKGROUND
[0002] At present, the proportion of lithium iron phosphate batteries in the power battery market has broken through 70%. The annual output of positive electrode materials is showing a sustained growth trend. With the strong support of national policies, the overall lithium battery recycling industry is showing a rapid development trend. However, electronic-grade iron phosphate and lithium iron phosphate materials have not yet achieved industrial application of regeneration technology due to strict technical index requirements and high industry technical barriers. Most related technical researches are still in the laboratory research stage, and only a few enterprises have entered the pilot test stage.
[0003] The mainstream process in the current lithium battery recycling field is still mainly directional separation of high-value metal elements. After the recovery of valuable components such as copper, aluminum, and lithium, the resource utilization rate of lithium extraction tailings has been at a low level for a long time. Some enterprises are limited by economic considerations of the main business and even take negative income disposal methods, and entrust third parties to clean up by paying disposal fees. At the same time, phosphate rock resources, as a key raw material for new energy materials, are facing severe challenges.
[0004] The main elements in lithium extraction tailings waste are phosphorus, iron, and carbon. Iron and phosphorus form a stable symbiotic structure in the form of iron phosphate crystals, and carbon exists in the form of nanoscale agglomerates or physical adsorption state and closely coexists with phosphorus-iron compounds. The core bottleneck of the difficulty in resource utilization of this kind of solid waste is that the efficient dissociation technology of phosphorus and iron elements has not been broken through. Under the industrial background of listing phosphate rock as a strategic mineral resource, its price continues to run at a high level, and the reserve-production ratio decreases year by year, developing directional dissociation technology of phosphorus, iron, and carbon in lithium extraction tailings to realize high-value recovery of phosphorus resources and replace phosphate rock for preparation of phosphate materials has become a dual urgent demand to break the solid waste disposal dilemma of the new energy industry and ensure the supply of strategic resources. SUMMARY
[0005] The present application relates to the technical field of battery material recycling, and particularly relates to a method for directly preparing phosphate at low temperature by using lithium extraction tailings.
[0006] In order to achieve the above-mentioned purpose, the technical scheme adopted by the present application is as follows:
[0007] A method for directly preparing phosphate at low temperature by using lithium extraction tailings, comprising the following steps:
[0008] S1, acidolysis of lithium extraction tailings at room temperature, followed by solid-liquid separation and washing to obtain filter wash liquid A and filter residue carbon powder;
[0009] S2, the filter washes liquid A and chlorinated salt at room temperature, and then extracts the reaction liquid to separate iron and phosphorus, to obtain a phosphorus-containing aqueous phase raffinate B and an iron-containing organic phase extract C;
[0010] S3, the phosphorus-containing aqueous phase raffinate B is concentrated, cooled, crystallized, and recrystallized to obtain pure phosphate;
[0011] S4, the iron-containing organic phase extract C is washed with water or back-extracted with hydrochloric acid or alkali to obtain a pure organic phase, iron salt or iron hydroxide and the corresponding salt;
[0012] S5, the pure phosphate obtained in step S3 is adjusted in pH value, and 1% of the mass of the phosphate is added to the reaction system after the pH value is adjusted. The pure organic phase in step S4 is reacted to obtain pure iron phosphate precipitate in the aqueous phase.
[0013] Preferably, in the step S1, 10% to 31% of hydrochloric acid is used to acidolysis lithium tailings, and the acidolysis time is 2.5 to 3.0 hours.
[0014] Preferably, in the step S2, the chlorinated salt is an alkali metal chloride, including sodium chloride, potassium chloride or ammonium chloride, and the molar ratio of the chlorinated salt to hydrochloric acid is not less than 1:3.
[0015] Preferably, in the step S2, the extractant selected in the extraction is composed of a main extractant and sulfonated kerosene, and the main extractant is selected from at least one of extractants N503, triisooctylamine N235 and tri-n-octylamine TOA, the volume ratio of the main extractant is 20% to 40%, and the volume ratio of the sulfonated kerosene is 60% to 80%.
[0016] Preferably, the volume ratio of the main extractant in the extractant is 30%, and the volume ratio of the sulfonated kerosene is 70%.
[0017] Preferably, in the step S2, the extraction operation adopts cross-flow extraction, and the extraction series is 8 to 12.
[0018] Preferably, in the step S3, the specific gravity of the concentrated solution is 1.38 to 1.48, and the crystallization temperature is 35℃.
[0019] Preferably, in the step S5, the pH value is adjusted to 6.5 to 7.5, and the obtained iron phosphate precipitate is subjected to hydrothermal reaction and calcination to prepare electronic-grade iron phosphate, wherein the hydrothermal reaction temperature is 95 to 98℃, the calcination temperature is 680 to 750℃, and the calcination time is 4 to 6 hours.
[0020] In the present application, the reaction principle is as follows:
[0021] FePO4+3HCl→FeCl3+H3PO4
[0022] In the process of dissolving iron phosphate (FePO4) with hydrochloric acid (HCl), iron is converted into ferric chloride (FeCl3), and phosphorus forms phosphoric acid (H3PO4), so that iron and phosphorus are both in the solution system.
[0023] NaCl+H3PO4→NaH2PO4+HCl
[0024] KCl+H3PO4→KH2PO4+HCl
[0025] By adding sodium chloride (NaCl) or potassium chloride (KCl) to the solution, phosphoric acid (H3PO4) is converted into dihydrogen phosphate (NaH2PO4 or KH2PO4). This accurately controls the pH value of the solution, creating suitable conditions for subsequent iron extraction and separation.
[0026] FeCl3+HCl+nR→[FeCl4]H·nR
[0027] In this process, R represents an organic extractant, such as TBP (trioctylphosphine oxide), which is commonly used and will not be described in detail. In a high concentration of chloride ion environment, trivalent iron ions (Fe³⁺) form a complex anion (FeCl4⁻) and combine with the extractant R to form a complex ([FeCl4] H・nR) that can dissolve in the organic phase. Through this reaction, iron can be transferred from the aqueous phase to the organic phase, thereby achieving separation from phosphorus.
[0028] 2[FeCl4]H·nR+Na2HPO4+NaH2PO4+4H2O→2FePO4·2H2O+nR+3NaCl
[0029] In this reaction, a mixed solution of disodium hydrogen phosphate (Na2HPO4) and sodium dihydrogen phosphate (NaH2PO4) is added to the iron-loaded organic phase, causing the iron ions to re-precipitate as iron phosphate (FePO4・2H2O). At the same time, the extractant R is regenerated and can be recycled.
[0030] The present application has the following beneficial effects:
[0031] 1. By means of crystallization or recrystallization, the purity of the phosphates in the aqueous raffinate is greatly improved, and the organic phase is washed with ultrapure water, which efficiently purifies the iron salts in the organic phase, thereby achieving the goal of high-value utilization of solid waste by preparing high-purity electronic-grade iron phosphate from lithium extraction tailings.
[0032] 2. After adjusting the pH of the reaction system, 1% (mass of phosphate) of the composite template is added, the porous structure formed by the dissolution of MgCO3 microspheres serves as a "template cavity", the carboxyl groups of CMC form a coordination network with Fe3+ and PO43-, guiding the uniform growth of iron phosphate, which can not only reduce the hydrothermal reaction temperature, but also narrow the particle size distribution of electronic-grade iron phosphate and improve the preparation rate. BRIEF DESCRIPTION OF DRAWINGS
[0033] Figure 1 A process flow chart of a method for directly preparing a phosphate at a low temperature using a lithium extraction tailing is provided.
[0034] Figure 2 An XRD pattern of a sample obtained in Example 1 of the present application;
[0035] Figure 3 An XRD pattern of a sample obtained in Example 4 of the present application;
[0036] Figure 4 A high width (FWHM) comparison chart of Example 1 and Example 4 in the present application. DETAILED DESCRIPTION
[0037] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments.
[0038] Example 1
[0039] A method for directly preparing a phosphate at a low temperature (not higher than 100 degrees) using a lithium extraction tailing, comprising the following steps:
[0040] ① N,N-bis(1-methylheptyl)acetamide N503 is used as a main extractant, accounting for 35% by volume, and a volume ratio of 65% of sulfonated kerosene is used as a ligand, and the two are mixed to obtain a mixed extractant O for iron.
[0041] ② 10% hydrochloric acid is used to acid hydrolyze the lithium extraction tailing at a room temperature for 2.5 hours according to a molar ratio of phosphorus P to hydrochloric acid HCl of 1:3, and then a filter press is used for pressure filtration and water washing to obtain carbon powder (according to the degree of graphitization, the carbon powder is sold to a negative electrode production factory or other users), and a filter washing liquid A is obtained at the same time.
[0042] ③ The filter washing liquid A is reacted with sodium chloride at a room temperature for 1 hour according to a molar ratio of 1:1 to obtain a reaction liquid.
[0043] ④ The reaction liquid is cross-flow extracted with the mixed extractant O at a room temperature for eight stages to obtain a phosphorus-containing aqueous phase raffinate B and an iron-containing organic phase extract C.
[0044] ⑤Concentrate the phosphorus-containing aqueous phase raffinate B to a specific gravity of 1.48, cool to 35 degrees, crystallize, and centrifugally separate to obtain pure sodium dihydrogen phosphate dihydrate, which is directly packaged and sold; or add sodium hydroxide to the concentrated liquid to adjust the pH to 6.50, filter and separate to obtain filter wash liquid E, which is used as a phosphorus source for the next step of synthesizing iron phosphate.
[0045] ⑥Wash the iron-containing organic phase extract C with ultrapure water 3 times according to a volume ratio of 1:10 to obtain pure organic phase F for use in the next step of the reaction; or continue to back extract the iron-containing organic phase extract C with 5% NaOH solution and pure water in sequence to obtain aqueous slurry E containing NaCl and Fe(OH)3precipitate, and recovered extractant O, which can be returned to step ④ for repeated use as an extractant.
[0046] ⑦Pressure filter and wash the aqueous slurry E to separate to obtain high-purity iron hydroxide and sodium chloride filter wash liquid, the former of which is directly packaged and sold or further processed into ferric chloride or ferrous chloride, and the latter of which is concentrated, crystallized, and separated to obtain NaCl, which is returned to the previous process for repeated use as an auxiliary agent for extracting iron.
[0047] ⑧React the filter wash liquid E obtained in the previous step and the pure organic phase F according to a ratio of 1:1 at room temperature to obtain organic phase O1and aqueous slurry G containing iron phosphate precipitate, pressure filter and backwash the aqueous slurry G with ultrapure water until the conductivity is <500 to obtain wet-based amorphous electronic iron phosphate, then perform hydrothermal reaction in a hydrochloric acid solution with a pH of 1.4 at a temperature of 95 degrees to obtain crystalline electronic-grade iron phosphate, and the crystalline iron phosphate separated by pressure filtration is dried and calcined at 680 degrees for 6 hours to obtain commercial battery-grade iron phosphate for sale.
[0048] Table 1-1 Analysis results of finished iron phosphate of Example 1
[0049] Item name Fe(%) P(%) Iron / Phosphorus Ca Cd Cr K Mg Mn Analysis result 36.42 21.01 0.961 73ppm 1.5ppm 20ppm 28ppm 24ppm 10ppm
[0050] Table 1-2 Analysis results of finished iron phosphate of Example 1
[0051] Item name Ni Pb Zn Al Co Na Cu Ti Analysis result 4ppm 16ppm 12ppm 20ppm 1ppm 48ppm 0 1741ppm
[0052] Wash the organic phase O1with pure water to obtain recovered extractant O, which is returned to step ④ for repeated use as an extractant to perform the operation of extracting iron again.
[0053] The phase composition of the sample was studied using a Rigaku MiniFlex600 X′Pert type X-ray diffractometer (Cu target, λ = 0.15405 nm); the iron element content of the sample was analyzed using a Netherlands Panalytical Axios type X fluorescence spectrometer, and the analysis results are shown in Table 1-1. Figure 2
[0054] Example 2
[0055] A method for directly preparing phosphate at low temperature using lithium extraction tailings, comprising the following steps:
[0056] ① N,N-bis(1-methylheptyl)acetamide N503 is used as the main extractant, accounting for 35% by volume, and 65% by volume of sulfonated kerosene is used as the auxiliary extractant, and the two are mixed as the mixed extractant O of iron.
[0057] ② 10% hydrochloric acid is used to acid hydrolyze the lithium extraction tailings at room temperature for 2.5 hours according to a molar ratio of phosphorus P to hydrochloric acid HCl of 1:3, and then pressure filtration and water washing are performed to obtain carbon powder (which is sold to battery negative production manufacturers or other users according to the degree of graphitization), and at the same time, a filter washing liquid A is obtained.
[0058] ③ The phosphorus in the filter washing liquid A and potassium chloride are reacted at a molar ratio of 1:1 at room temperature for 1 hour to obtain a reaction liquid.
[0059] ④ The reaction liquid and the mixed extractant O are cross-flow extracted at room temperature for eight stages to obtain a phosphorus-containing aqueous raffinate B and an iron-containing organic phase extract C.
[0060] ⑤ The phosphorus-containing aqueous raffinate B is concentrated to a specific gravity of 1.38, cooled to 35 degrees, crystallized, and centrifuged to obtain pure potassium dihydrogen phosphate, which is directly packaged and sold; or potassium hydroxide is added to adjust the pH value to 6.50, and a filter washing liquid E is obtained by filtration and separation, which is used as a phosphorus source for the next step of synthesizing iron phosphate.
[0061] ⑥ The iron-containing organic phase extract C is washed with ultrapure water three times according to a volume ratio of 1:10 to obtain a pure organic phase F for the next step of reaction; or the iron-containing organic phase extract C is back-extracted with 5% KOH solution and pure water in turn to obtain a water phase slurry E containing KCl and Fe(OH)3 precipitate, and a recovered extractant O, which can be returned to step ④ for repeated use as an extractant.
[0062] ⑦ The slurry E is subjected to pressure filtration and washing separation to obtain high-purity iron hydroxide and potassium chloride filter washing liquid, the former is directly packaged and sold or further processed into ferric chloride or ferrous chloride, and the latter is concentrated, crystallized, and separated to obtain KCl, which is returned to the previous process for repeated use as an auxiliary agent for extracting iron.
[0063] ⑧The filtrate E obtained in the previous step and the pure organic phase F are reacted at a ratio of 1:1 at room temperature to obtain an organic phase O1 and an aqueous slurry G containing iron phosphate precipitate. The aqueous slurry G is pressure-filtered and washed with ultrapure water until the conductivity is less than 500, to obtain wet-based amorphous electronic iron phosphate. The wet-based amorphous electronic iron phosphate is then subjected to hydrothermal reaction in a hydrochloric acid solution at pH 1.4 and at 95°C to obtain crystalline electronic-grade iron phosphate. The crystalline iron phosphate separated by pressure filtration is dried and calcined at 680°C for 6 hours to obtain commercial battery-grade iron phosphate.
[0064] Table 2-1 Analysis results of finished iron phosphate of Example 2
[0065] Item name Fe(%) P(%) Iron / Phosphorus Ca Cd Cr K Mg Mn Analysis result 36.13 20.77 0.965 74ppm 2ppm 19ppm 30ppm 25ppm 9ppm
[0066] Table 2-2 Analysis results of finished iron phosphate of Example 2
[0067] Item name Ni Pb Zn Al Co Na Cu Ti Analysis result 5ppm 18ppm 9ppm 21ppm 0 45ppm 0 1749ppm
[0068] The organic phase O1 is washed with pure water to obtain recovered extractant O, which is returned to step ④ for reuse as an extractant, and the operation of extracting iron is repeated.
[0069] Example 3
[0070] The filtrate E obtained in the previous step and the pure organic phase F are reacted at a ratio of 1:1 at room temperature to obtain an organic phase O1 and an aqueous slurry G containing iron phosphate precipitate. The G is pressure-filtered and washed with ultrapure water until the conductivity is less than 500, to obtain wet-based amorphous electronic iron phosphate. The wet-based amorphous electronic iron phosphate is then subjected to hydrothermal reaction in a hydrochloric acid solution at pH 1.4 and at 95°C to obtain crystalline electronic-grade iron phosphate. The crystalline iron phosphate separated by pressure filtration is dried and calcined at 680°C for 6 hours to obtain commercial battery-grade iron phosphate.
[0071] ① Triisooctylamine N235 is used as the main extractant, accounting for 30% by volume, and 70% by volume of sulfonated kerosene is used as the ligand. The two are mixed and used as the mixed extractant O for iron.
[0072] ② The lithium extraction tailings are acid hydrolyzed with 10% hydrochloric acid at room temperature for 3.0 hours according to a molar ratio of phosphorus P to HCl of 1:3. The hydrolyzed tailings are then pressure-filtered and washed with water to obtain carbon powder (which is sold to battery anode manufacturers or other users according to the degree of graphitization), and a filtrate A is obtained.
[0073] ③ The filtrate A is reacted with sodium chloride at a molar ratio of 1:1 at room temperature for 1 hour to obtain a reaction solution.
[0074] ④ The reaction solution is cross-flow extracted with the mixed extractant O for 12 stages at room temperature to obtain a phosphorus-containing aqueous raffinate B and an iron-containing organic phase extract C.
[0075] ⑤Concentrate the phosphorus-containing aqueous phase raffinate B to a specific gravity of 1.48, cool to 35 degrees, crystallize, centrifuge to obtain pure sodium dihydrogen phosphate dihydrate, which is directly packaged and sold; or add sodium hydroxide to adjust the pH value to 6.50, filter to obtain filter wash E, which is used as a phosphorus source for the next step of synthesizing iron phosphate.
[0076] ⑥Wash the iron-containing organic phase extract C with ultrapure water 2 times according to a volume ratio of 1:10 to obtain pure organic phase F; or continue to back extract the iron-containing organic phase extract C with 5% NaOH solution and pure water in turn to obtain aqueous slurry E containing NaCl and Fe(OH)3 precipitate, and recovered extractant O, which can be returned to step ④ for repeated use as an extractant.
[0077] ⑦Filter and wash slurry E to obtain high-purity iron hydroxide and sodium chloride filter wash, the former of which is directly packaged and sold or further processed into ferric chloride or ferrous chloride, and the latter of which is concentrated and crystallized to obtain NaCl, which is returned to the previous process for repeated use as an auxiliary agent for extracting iron.
[0078] ⑧React filter wash E and pure organic phase F obtained in the previous step at room temperature according to a ratio of 1:1 to obtain organic phase O1 and aqueous slurry G containing iron phosphate precipitate, filter and wash G with ultrapure water to a conductivity of <500 to obtain wet-based amorphous electronic iron phosphate, and perform hydrothermal reaction in a hydrochloric acid solution with a pH of 1.4 at 95 degrees to obtain crystalline electronic-grade iron phosphate, which is dried, calcined at 680 degrees for 6 hours to obtain commercial battery-grade iron phosphate for sale.
[0079] Table 3-1 Analysis results of finished iron phosphate of Example 3
[0080] Item name Fe(%) P(%) Iron / Phosphorus Ca Cd Cr K Mg Mn Analysis result 35.97 20.62 0.967 77ppm 1ppm 18ppm 29ppm 28ppm 13ppm
[0081] Table 3-2 Analysis results of finished iron phosphate of Example 3
[0082] Item name Ni Pb Zn Al Co Na Cu Ti Analysis result 8ppm 15ppm 10ppm 24ppm 0 42ppm 0.2ppm 1753ppm
[0083] Wash organic phase O1 with pure water to obtain recovered extractant O, which is returned to step ④ for repeated use as an extractant for extracting iron.
[0084] Example 4
[0085] A method for directly preparing phosphates at low temperature using lithium extraction tailings, comprising the following steps:
[0086] ① Use triisooctylamine N235 as the main extractant, with a volume ratio of 30%, and mix with 70% sulfonated kerosene by volume to obtain a mixed extractant O for iron.
[0087] ②According to the molar ratio of phosphorus P to HCl 1:3, the lithium extraction tailings are acid hydrolyzed with 10% hydrochloric acid at room temperature for 2.5 hours, then filtered and washed with water to obtain carbon powder (sold to battery negative electrode manufacturers or other users according to the degree of graphitization value), and at the same time, filter washing liquid A is obtained.
[0088] ③The filter washing liquid A is reacted with potassium chloride at a molar ratio of 1:1 at room temperature for 1 hour to obtain a reaction liquid.
[0089] ④The reaction liquid is cross-flow extracted with mixed extractant O at room temperature for twelve stages to obtain phosphorus-containing aqueous raffinate B and iron-containing organic phase extract C.
[0090] ⑤The phosphorus-containing aqueous raffinate B is concentrated to a specific gravity of 1.48, cooled to 35 degrees, and crystallized, and then centrifuged to obtain pure potassium dihydrogen phosphate, which is directly packaged and sold; or the pH value is adjusted to 7.00 with KOH, and then filtered and separated to obtain filter washing liquid E, which is used as a phosphorus source for synthesizing iron phosphate in the next step.
[0091] ⑥The iron-containing organic phase extract C is washed twice with ultrapure water at a volume ratio of 1:10 to obtain pure organic phase F, or the iron-containing organic phase extract C is further back-extracted with 5% KOH solution and pure water to obtain water phase slurry E containing KCl and Fe(OH)3 precipitate, and recovered extractant O, which can be returned to step ④ for repeated use as an extractant.
[0092] ⑦The slurry E is filtered and washed to obtain high-purity iron hydroxide and potassium chloride filter washing liquid, the former is directly packaged and sold or further processed into ferric chloride or ferrous chloride, and the latter is concentrated and crystallized to obtain KCl, which is returned to the previous process as an auxiliary agent for extracting iron.
[0093] ⑧The filter washing liquid E and the pure organic phase F obtained in the previous step are reacted at a ratio of 1:1 at room temperature to obtain organic phase O1 and water phase slurry G containing iron phosphate precipitate, which is filtered and washed with ultrapure water until the conductivity is <500 to obtain wet-based amorphous electronic iron phosphate, and in the pH 1.4 hydrochloric acid solution, a composite template accounting for 1% of the mass of the phosphate is added to the reaction system after adjusting the pH.
[0094] The composite template is prepared as follows:
[0095] Carbonate magnesium microspheres are prepared by mixing equal volumes of 0.5 mol / L MgCl2 solution and 0.5 mol / L Na2CO3 solution at 50°C, stirring for 1 hour to form MgCO3・3H2O microspheres;
[0096] Surface carboxylation: MgCO3 microspheres were mixed with sodium chloroacetate at a molar ratio of 1:2 and reacted in an aqueous solution at pH = 10 at 60°C for 3 hours to introduce carboxyl groups;
[0097] Carboxymethyl cellulose grafting: carboxylated MgCO3 was mixed with CMC at a mass ratio of 1:3 and reacted at room temperature for 4 hours under EDC / NHS catalysis to form a CMC-MgCO3 composite template;
[0098] Pore regulation: the composite template was soaked in 0.1 mol / L hydrochloric acid for 1 hour to partially dissolve MgCO3 and form a porous structure;
[0099] Washing and drying: washed with deionized water until neutral, and dried at 60°C under vacuum to obtain a template powder
[0100] The hydrothermal reaction was carried out at 98 degrees to obtain crystalline electronic-grade iron phosphate. The crystal iron phosphate separated by pressure filtration was dried and calcined at 750 degrees for 4 hours to obtain commercial battery-grade iron phosphate for sale.
[0101] The phase composition of the sample was studied by a Rigaku MiniFlex600X′Pert X-ray diffractometer (Cu target, λ = 0.15405 nm); the iron element content of the sample was analyzed by a Netherlands Panalytical Axios X fluorescence spectrometer, and the analysis results are shown in Figure 4 .
[0102] Compared with Example 1, the crystallinity
[0103] The intensity of the (020) diffraction peak of Example 1 is low (350 counts), and the full width at half maximum (FWHM) is 0.45°, indicating that the crystal grows along the b-axis with high disorder. There is a small amount of amorphous diffraction package (2θ = 20°~25°), and the crystallinity is about 82% (calculated based on jade software).
[0104] For Example 4, the (020) peak intensity is significantly increased to 620 counts (+77.1%), and the half width is narrowed to 0.32°, indicating that the composite template guides the preferential growth of the crystal along the (020) plane. The amorphous package disappears, and the crystallinity is increased to 94%, which confirms that the composite template promotes the complete growth of the crystal by “porous cavity limitation + coordination guidance”.
[0105] Further, for the crystal face orientation analysis
[0106] The intensity of the (020) peak of Example 4 is increased from 21% of Example 1 to 34%, indicating that the CMC carboxyl group in the composite template forms a coordination bond with Fe³⁺, guiding the oriented deposition of iron phosphate along the (020) crystal plane, which is consistent with the direction of the layered pore of the MgCO3 template.
[0107] Further, the full width at half maximum (FWHM) of the samples obtained in Example 1 and Example 4 were compared and analyzed, as shown in Table 1. Figure 4 As shown, the full width at half maximum (FWHM) is a key indicator for evaluating the quality of crystals in XRD patterns, and the smaller the value, the higher the crystallinity and the fewer the defects. The FWHM was generally reduced: the FWHM of all characteristic peaks in Example 4 was significantly lower than that in Example 1, with an average improvement rate of 25.8%
[0108] The high-angle region was optimized more obviously: the FWHM improvement rate in the region above 70° was more than 25%, indicating that the composite template had a more significant effect on the order of high-order crystal faces
[0109] The (020) crystal plane was optimized prominently: the FWHM at 20.3° was reduced from 0.45° to 0.32°, with an improvement rate of 28.9%, confirming the directional guiding effect of the template on the growth of b-axis direction crystals.
[0110] Therefore, in Example 4, the composite template prepared by adding relevant processes was added to the reaction system after adjusting the pH, which could achieve the following technical effects:
[0111] Improved crystallinity: the general reduction of FWHM indicates a decrease in the internal defect density of the crystal and a significant improvement in the integrity of the crystal
[0112] Crystal growth regulation: by regulating the growth rate of specific crystal planes through the template, the size of the crystal grains was increased
[0113] Directional growth evidence: the (020) crystal plane has the highest FWHM improvement rate, which is consistent with the increase in the intensity of this crystal plane in the XRD intensity data.
[0114] Table 4-1 Analysis results of finished iron phosphate product in Example 4
[0115] Item name Fe(%) P(%) Iron / Phosphorus Ca Cd Cr K Mg Mn Analysis result 35.79 20.38 0.979 70ppm 3ppm 23ppm 35ppm 21ppm 8ppm
[0116] Table 4-2 Analysis results of finished iron phosphate product in Example 4
[0117] Item name Ni Pb Zn Al Co Na Cu Ti Analysis result 6ppm 22ppm 8ppm 23ppm 1ppm 44ppm 0 1735ppm
[0118] The organic phase O1 was washed with pure water to obtain the recovered extractant O, which was returned to step ④ for repeated use as an extractant for iron extraction.
[0119] Example 5
[0120] A method for directly preparing phosphates at low temperature using lithium extraction tailings, comprising the following steps:
[0121] ① Use tri-n-octylamine TOA as the main extractant, with a volume ratio of 30%, and mix with 70% sulfonated kerosene by volume to obtain a mixed extractant O for iron extraction.
[0122] 2. The lithium extraction residue is acid hydrolyzed with 10% hydrochloric acid at room temperature for 3.0 hours at a molar ratio of phosphorus P to hydrochloric acid 1:3, and then filtered and washed with water to obtain carbon powder (which is sold to battery cathode manufacturers or other users according to the degree of graphitization) and a filtrate A.
[0123] 3. The filtrate A is reacted with sodium chloride at a molar ratio of 1:1 at room temperature for 1 hour to obtain a reaction solution.
[0124] 4. The reaction solution is extracted with mixed extractant O at room temperature for 12 stages to obtain a phosphorus-containing aqueous raffinate B and an iron-containing organic phase extract C.
[0125] 5. The phosphorus-containing aqueous raffinate B is concentrated to a specific gravity of 1.48, cooled to 35 degrees, and crystallized to obtain pure sodium dihydrogen phosphate dihydrate, which is directly packaged and sold; or sodium hydroxide is added to adjust the pH value to 6.50, and a filtrate E is obtained by filtration and separation, which is used as a phosphorus source for synthesizing iron phosphate in the next step.
[0126] 6. The iron-containing organic phase extract C is washed twice with ultrapure water at a volume ratio of 1:10 to obtain a pure organic phase F, or the iron-containing organic phase extract C is back-extracted with 5% NaOH solution and pure water in sequence to obtain a water phase slurry E containing NaCl and Fe(OH)3 precipitate, and a recovered extractant O, which can be returned to step 4 for repeated use as an extractant.
[0127] 7. The slurry E is filtered and washed to obtain high-purity iron hydroxide and sodium chloride filtrate, the former of which is directly packaged and sold or further processed into ferric chloride or ferrous chloride, and the latter of which is concentrated and crystallized to obtain NaCl, which is returned to the previous process as an auxiliary agent for extracting iron.
[0128] 8. The filtrate E obtained in the previous step and the pure organic phase F are reacted at a ratio of 1:1 at room temperature to obtain an organic phase O1 and a water phase slurry G containing iron phosphate precipitate, which is filtered and washed with ultrapure water until the conductivity is <500 to obtain wet-based amorphous electronic iron phosphate, which is hydrothermally reacted in a hydrochloric acid solution at pH 1.4 at 96 degrees to obtain crystalline electronic-grade iron phosphate, which is separated by filtration, dried, calcined at 700 degrees for 5 hours to obtain commercial battery-grade iron phosphate.
[0129] Table 5-1 Analysis results of finished iron phosphate of Example 5
[0130] Item name Fe(%) P(%) Iron / Phosphorus Ca Cd Cr K Mg Mn Analysis result 36.58 20.96 0.968 72ppm 2.5ppm 19ppm 26ppm 30ppm 12ppm
[0131] Table 5-2 Analysis results of finished iron phosphate of Example 5
[0132] Item name Ni Pb Zn Al Co Na Cu Ti Analysis result 3ppm 19ppm 14ppm 25ppm 0 51ppm 0.5ppm 1739ppm
[0133] The organic phase O1 is washed with pure water to obtain the recovered extractant O, which is returned to step 4 to be reused as the extractant for the extraction of iron.
Claims
1. A method for directly preparing phosphate at low temperature using lithium extraction tailings, characterized in that, It comprises the following steps: S1, acidolysis of lithium extraction tailings at room temperature, followed by solid-liquid separation and washing to obtain filter wash liquid A and filter residue carbon powder; S2, reacting filter wash liquid A with a chlorinated salt at room temperature, and then separating iron and phosphorus by extraction of the reaction liquid to obtain phosphorus-containing aqueous phase raffinate B and iron-containing organic phase extract C; S3, concentrating, cooling, crystallizing and recrystallizing the phosphorus-containing aqueous phase raffinate B to obtain pure phosphate; S4, water washing or back extraction with hydrochloric acid or alkali to obtain pure organic phase, iron salt or iron hydroxide and corresponding salt; S5, adjusting the pH value of the pure phosphate obtained in step S3, adding 1% of the mass of the phosphate of a composite template to the reaction system after adjusting the pH value, and finally reacting with the pure organic phase in step S4 to obtain pure iron phosphate precipitate in the aqueous phase.
2. The method for directly preparing phosphate at low temperature by using the lithium extraction tailings according to claim 1, characterized in that, In step S1, 10% to 31% hydrochloric acid is used to acidolysis lithium extraction tailings, and the acidolysis time is 2.5 to 3.0 hours.
3. The method for directly preparing phosphate at low temperature by using the lithium extraction tailings according to claim 2, characterized in that, In step S2, the chlorinated salt is an alkali metal chloride, including sodium chloride, potassium chloride or ammonium chloride, and the molar ratio of the chlorinated salt to hydrochloric acid is not less than 1:
3.
4. The method for directly preparing phosphate at low temperature by using the lithium extraction tailings according to claim 1, characterized in that, In step S5, the composite template is prepared by the following method: Preparation of magnesium carbonate microspheres: Mix 0.5 mol / L MgCl2 solution and 0.5 mol / L Na2CO3 solution in equal volumes at 50°C, stir for 1 hour to form MgCO3·3H2O microspheres; Surface carboxylation: Mix MgCO3 microspheres and sodium chloroacetate at a molar ratio of 1:2 in an aqueous solution at pH=10, and react at 60°C for 3 hours to introduce carboxyl groups; Carboxymethyl cellulose grafting: Mix carboxylated MgCO3 and CMC at a mass ratio of 1:3, and react at room temperature for 4 hours under EDC / NHS catalysis to form CMC-MgCO3 composite template; Pore regulation: Soak the composite template in 0.1 mol / L hydrochloric acid for 1 hour to partially dissolve MgCO3 and form a porous structure; Washing and drying: Wash with deionized water until neutral, and vacuum dry at 60°C to obtain template powder.
5. The method for directly preparing phosphate at low temperature by using the lithium extraction tailings according to claim 1, characterized in that, In step S2, the extractant selected for extraction is composed of a main extractant and sulfonated kerosene, and the main extractant is selected from at least one of extractants N503, triisooctylamine N235 and tri-n-octylamine TOA, with the main extractant accounting for 20% to 40% by volume and the sulfonated kerosene accounting for 60% to 80% by volume.
6. The method for preparing phosphate at low temperature directly using the lithium extraction tailings according to claim 5, characterized in that, In the extractant, the main extractant accounts for 30% by volume and the sulfonated kerosene accounts for 70% by volume.
7. The method for directly preparing phosphate at low temperature by using the lithium extraction tailings according to claim 1, characterized in that, In step S2, cross-flow extraction is used for extraction, and the extraction stage number is 8 to 12. 8.The method for preparing phosphate at low temperature directly using the lithium extraction tailings according to claim 1, characterized in that, In step S3, the specific gravity of the concentrated solution is 1.38 to 1.48, and the crystallization temperature is 35°C. 9.The method for preparing phosphate at low temperature directly using the lithium extraction tailings according to claim 1, characterized in that, In step S4, after back extraction, the pure organic phase is returned to step S2 for use as an extractant. 10.The method for preparing phosphate at low temperature directly using the lithium extraction tailings according to claim 1, characterized in that, In step S5, the pH value is adjusted to 6.5 to 7.5, and the obtained iron phosphate precipitate is subjected to hydrothermal reaction and calcination to obtain electronic-grade iron phosphate, wherein the hydrothermal reaction temperature is 95 to 98°C, the calcination temperature is 680 to 750°C, and the calcination time is 4 to 6 hours.